If the Iraqi population is "threatened by the use of force outside the law, then we will intervene militarily," he said.

Iraq's Kurdish region plans to hold the referendum on support for independence from Iraq on Sept. 25 in three governorates that make up their autonomous region, and in disputed areas controlled by Kurdish forces but which are claimed by Baghdad.

"If you challenge the constitution and if you challenge the borders of Iraq and the borders of the region, this is a public invitation to the countries in the region to violate Iraqi borders as well, which is a very dangerous escalation," al-Abadi said.

The leaders of Iraq's Kurdish region have said they hope the referendum will push Baghdad to come to the negotiating table and create a path for independence. However, al-Abadi said such negotiations would likely be complicated by the referendum vote.

"It will make it harder and more difficult," he said, but added, "I will never close the door to negotiations. Negotiations are always possible."

Iraq's Kurds have come under increasing pressure to call off the vote from regional powers and the United States, a key ally, as well as Baghdad.

In a statement released late Friday night the White House called for the Kurdish region to abandon the referendum "and enter into serious and sustained dialogue with Baghdad."

"Holding the referendum in disputed areas is particularly provocative and destabilizing," the statement read.

Tensions between Irbil and Baghdad have flared in the lead-up to the Sept. 25 vote.

Masoud Barzani, the president of Iraq's autonomous Kurdish region, has repeatedly threatened violence if Iraqi military or Shiite militias attempt to move into disputed territories that are now under the control of Kurdish fighters known as Peshmerga, specifically the oil-rich city of Kirkuk.

"It's chaotic there," Muhammad Mahdi al-Bayati, a senior leader of Iraq's mostly Shiite fighters known as the popular mobilization forces, said earlier this week, describing Kirkuk in the lead up to the vote.

Al-Bayati's forces — sanctioned by Baghdad, but many with close ties to Iran — are deployed around Kirkuk as well as other disputed territories in Iraq's north.

"Everyone is under pressure," he said, explaining that he feared a rogue group of fighters could trigger larger clashes. "Anything could be the spark that burns it all down."

Al-Abadi said he is focused on legal responses to the Kurdish referendum on independence. Earlier this week Iraq's parliament rejected the referendum in a vote boycotted by Kurdish lawmakers.

Iraq's Kurds have long held a dream of statehood. Brutally oppressed under Saddam Hussein, whose military in the 1980s killed at least 50,000 of them, many with chemical weapons, Iraq's Kurds established a regional government in 1992 after the U.S. enforced a no-fly zone across the north following the Gulf War.

After the 2003 U.S.-led invasion ousted Saddam, the region secured
constitutional
recognition of its autonomy, but remained part of the Iraqi state.

When asked if he would ever accept an independent Kurdistan, Al-Abadi said, "It's not up to me, this is a
constitutional
" matter.

"If (Iraq's Kurds) want to go along that road, they should work toward amending the constitution," al-Abadi said. "In that case we have to go all the way through parliament and a referendum to the whole Iraqi people.

"For them to call for only the Kurds to vote, I think this is a hostile move toward the whole of the Iraqi population," he said.

Al-Abadi began his term as prime minister after Mosul had fallen to IS, plunging Iraq into the deepest political and security crisis since the sectarian bloodshed that followed the 2003 U.S.-led invasion.

Over the past three years, Iraqi forces have slowly clawed back territory from the extremist group and al-Abadi has used the battlefield victories to garner public support.

However the military successes have come at great cost. In the fight for Mosul alone between 970 and 1,260 civilians were killed and more than twice as many members of Iraq's security forces lost their lives, al-Abadi told the AP Saturday.

Despite territorial losses, IS continues to carry out insurgency-style attacks in Iraq.

Thursday, an attack claimed by IS at a checkpoint and restaurant in southern Iraq left more than 80 killed and 93 wounded.

Years of war have left more than 3 million people displaced. Cities, towns and villages retaken from IS lie in ruins and the forces made powerful by the arms and training that flooded Iraq to fight the extremists are now attempting to leverage that influence.

Al-Abadi said he's confident the security and economic situation in Iraq will continue to improve.

Regarding his ambitious package of political and economic reforms initially introduced in 2015, al-Abadi said, "I think we've achieved some," but added, "It will take time."

Despite the challenges ahead, al-Abadi repeated a call for Iraqis who fled the country over the past three years, to return home. Some 80,000 Iraqis made the treacherous journey to Europe by sea in 2015 alone, according to the United Nations.

"I'm not going to support forced repatriation into Iraq but I think all of Iraqis, they found it very tough to be in Europe as refugees," al-Abadi said, explaining he is in "lengthy negotiations" with his counterparts in Europe to aid the return of refugees.

"These are Iraqi people. We don't want to lose our citizens," he said.